Precipitation is the creation of a solid in a solution or inside another solid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid solution, the solid formed is called the 'precipitate'.The chemical that causes the solid to form is called the 'precipitant'. Without sufficient force of gravity (settling) to bring the solid particles together, the precipitate remains in suspension. After sedimentation, especially when using a centrifuge to press it into a compact mass, the precipitate may be referred to as a 'pellet'. The precipitate-free liquid remaining above the solid is called the 'supernate' or 'supernatant'. Powders derived from precipitation have also historically been known as 'flowers'.

Sometimes the formation of a precipitate indicates the occurrence of a chemical reaction. If silver nitrate solution is poured into a solution of sodium chloride, a chemical reaction occurs forming a white precipitate of silver chloride. When potassium iodide solution reacts with lead nitrate solution, a yellow precipitate of lead iodide is formed.

Precipitation may occur if the concentration of a compound exceeds its solubility (such as when mixing solvents or changing their temperature). Precipitation may occur rapidly from a supersaturated solution.

In solids, precipitation occurs if the concentration of one solid is above the solubility limit in the host solid, due to e.g. rapid quenching or ion implantation, and the temperature is high enough that diffusion can lead to segregation into precipitates. Precipitation in solids is routinely used to synthesize nanoclusters.

An important stage of the precipitation process is the onset of nucleation. The creation of a hypothetical solid particle includes the formation of an interface, which requires some energy based on the relative surface energy of the solid and the solution. If this energy is not available, and no suitable nucleation surface is available, supersaturation occurs.

Precipitation reactions can be used for making pigments, removing salts from water in water treatment, and in classical qualitative inorganic analysis.

Precipitation is also useful to isolate the products of a reaction during workup. Ideally, the product of the reaction is insoluble in the reaction solvent. Thus, it precipitates as it is formed, preferably forming pure crystals. An example of this would be the synthesis of porphyrins in refluxing propionic acid. By cooling the reaction mixture to room temperature, crystals of the porphyrin precipitate, and are collected by filtration.

Precipitation may also occur when an antisolvent (a solvent in which the product is insoluble) is added, drastically reducing the solubility of the desired product. Thereafter, the precipitate may easily be separated by filtration, decanting, or centrifugation). An example would be the synthesis of chromic tetraphenylporphyrin chloride: water is added to the DMF reaction solution, and the product precipitates.[3] Precipitation is also useful in purifying products: crude bmim-Cl is taken up in acetonitrile, and dropped into ethyl acetate, where it precipitates.[4] Another important application of an antisolvent is in ethanol precipitation of DNA.

DNA stores biological information. The DNA backbone is resistant to cleavage, and both strands of the double-stranded structure store the same biological information. Biological information is replicated as the two strands are separated. A significant portion of DNA (more than 98% for humans) is non-coding, meaning that these sections do not serve as patterns for protein sequences.

The two strands of DNA run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes biological information. Under the genetic code, RNA strands are translated to specify the sequence of amino acids within proteins. These RNA strands are initially created using DNA strands as a template in a process called transcription.

Within cells, DNA is organized into long structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts.[1] In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.

First isolated by Friedrich Miescher in 1869 and with its molecular structure first identified by James Watson and Francis Crick in 1953, DNA is used by researchers as a molecular tool to explore physical laws and theories, such as the ergodic theorem and the theory of elasticity. The unique material properties of DNA have made it an attractive molecule for material scientists and engineers interested in micro- and nano-fabrication. Among notable advances in this field are DNA origami and DNA-based hybrid materials.

The obsolete synonym "desoxyribonucleic acid" may occasionally be encountered, for example, in pre-1953 genetics.

Genetics is the study of genes — what they are, what they do, and how they work. Genes are made up of molecules inside the nucleus of a cell that are strung together in such a way that the sequence carries information: that information determines how living organisms inherit phenotypic traits, (features) determined by the genes they from their parents and thereby going back through the generations. For example, offspring produced by sexual reproduction usually look similar to each of their parents because they have inherited some of each of their parents' genes. Genetics identifies which features are inherited, and explains how these features pass from generation to generation. In addition to inheritance, genetics studies how genes are turned on and off to control what substances are made in a cell - gene expression; and how a cell divides - mitosis or meiosis.

Some phenotypic traits can be seen, such as eye color while others can only be detected, such as blood type or intelligence. Traits determined by genes can be modified by the animal's surroundings (environment): for example, the general design of a tiger's stripes is inherited, but the specific stripe pattern is determined by the tiger's surroundings. Another example is a person's height: it is determined by both genetics and nutrition.

Genes are made of DNA, which is divided into separate pieces called chromosomes. Humans have 46: 23 pairs, though this number varies between species, for example many primates have 24 pairs. Meiosis creates special cells, sperm in males and eggs in females, which only have 23 chromosomes and it only when these two cells merge into one during the fertilization stage of sexual reproduction, creating a zygote and where a nucleic acid double helix divides, with each single helix occupies one of the daughter cells, resulting in half the normal number of genes. The zygote thendivides into four daughter cells by which time genetic recombination has created a new embryo with 23 pairs of chromosomes, half from each parent. Mating and resultant mate choice result in sexual selection. In normal cell division (mitosis) is possible when the double helix separates, and a complement of each separated half is made, resulting in two identical double helices in one cell, with each occupying one of the two new daughter cells created when the cell divides.

Chromosomes all contain four nucleotides, abbreviated C (cytosine), G (guanine), A (adenine), or T (thymine), which line up in a particular sequence and make a long string. There are two strings of nucleotides coiled around one another in each chromosome: a double helix. C on one string is always opposite from G on the other string; A is always opposite T. There are about 3.2 billion nucleotide pairs on all the human chromosomes: this is the human genome. The order of the nucleotides carries genetic information, whose rules are defined by the genetic code, similar to how the order of letters on a page of text carries information. Three nucleotides in a row - a triplet - carry one unit of information: a codon.

The genetic code not only controls inheritance: it also controls gene expression, which occurs when a portion of the double helix is uncoiled, exposing a series of the nucleotides, which are within the interior of the DNA. This series of exposed triplets (codons) carries the information to allow machinery in the cell to "read" the codons on the exposed DNA, which results in the making of RNA molecules. RNA in turn makes either amino acids or microRNA, which are responsible for all of the structure and function of a living organism; i.e. they determine all the features of the cell and thus the entire individual. Closing the uncoiled segment turns off the gene.

Within a species, the information in a given gene is not always exactly the same in every individual in that species, so the same gene in different individuals does not give exactly the same instructions. Each unique form of a single gene is called an allele; different forms are collectively called polymorphisms. As an example, one allele for the gene for hair color and skin cell pigmentation could instruct the body to produce black pigment, producing black hair and pigmented skin; while a different allele of the same gene in a different individual could give garbled instructions that would result in a failure to produce any pigment, giving white hair and no pigmented skin: albinism. Mutations are random changes in genes creating new alleles, which in turn produce new traits, which could help, harm, or have no new effect on the individual's likelihood of survival; thus, mutations are the basis for evolution.

Alchemy is an influential tradition whose practitioners have, from antiquity, claimed it to be the precursor to profound powers. As described by Paul-Jacques Malouin in The Encyclopedia of Diderot it is the chemistry of the subtlest kind which allows one to observe extraordinary chemical operations at a more rapid pace-ones that require a long time for nature to produce.[1] Definitions of the objectives of alchemy are varied but historically have typically included one or more of the following goals: the creation of the fabled philosopher's stone; the ability to transmute base metals into the noble metals (gold or silver); and development of an elixir of life, which would confer youth and longevity.

Though alchemy played a significant role in the development of early modern science, it differs significantly from modern science in its inclusion of Hermetic principles and practices related to mythology, magic, religion, and spirituality. It is recognized as a protoscience that contributed to the development of modern chemistry and medicine. Alchemists developed a structure of basic laboratory techniques, theory, terminology, and experimental method, some of which are still in use today. However, alchemists predated modern foundations of chemistry, such as scientific skepticism, atomic theory, the modern understanding of a chemical element and a chemical substance, the periodic table and conservation of mass and stoichiometry. Instead, they believed in four elements, and cryptic symbolism and mysticism was an integral part of alchemical work.

The ostensible goals of alchemy are often given as the transmutation of common metals into gold (known as chrysopoeia), the creation of a panacea, and the discovery of a universal solvent.[3] However, these only highlight certain aspects of alchemy. Alchemists have historically rewritten and evolved their explanation of alchemy, so it is difficult to define it simply.[4] H.J. Sheppard gives the following as a comprehensive summary:

    Alchemy is the art of liberating parts of the Cosmos from temporal existence and achieving perfection which, for metals is gold, and for man, longevity, then immortality and, finally, redemption. Material perfection was sought through the action of a preparation (Philosopher's Stone for metals; Elixir of Life for humans), while spiritual ennoblement resulted from some form of inner revelation or other enlightenment (Gnosis, for example, in Hellenistic and western practices).[5]

Modern discussions of alchemy are generally split into an examination of its exoteric practical applications and its esoteric aspects. The former is pursued by historians of the physical sciences who have examined the subject in terms of protochemistry, medicine, and charlatanism. The latter interests psychologists, spiritual and new age communities, hermetic philosophers, and historians of esotericism. The subject has also made an ongoing impact on literature and the arts. Despite the modern split, numerous sources stress an integration of esoteric and exoteric approaches to alchemy. Holmyard, when writing on exoteric aspects, states that they cannot be properly appreciated if the esoteric is not always kept in mind.[7] The prototype for this model can be found in Bolos of Mendes's 3rd-century BCE work Physika kai Mystika ("On Physical and Mystical Matters"). Marie-Louise von Franz tells us the double approach of Western alchemy was set from the start, when Greek philosophy was mixed with Egyptian and Mesopotamian technology. The technological, operative approach, which she calls extraverted, and the mystic, contemplative, psychological one, which she calls introverted, are not mutually exclusive but complementary since meditation requires practice in the real world and vice versa.

The start of Western alchemy may generally be traced to Hellenistic Egypt, where the city of Alexandria was a center of alchemical knowledge, and retained its pre-eminence through most of the Greek and Roman periods.[30] Here, elements of technology, religion, mythology, and Hellenistic philosophy, each with their own much longer histories, combined to form the earliest known records of alchemy in the West. Zosimos of Panopolis wrote the oldest known books on alchemy,[citation needed] while Mary the Jewess is credited as being the first non-fictitious Western alchemist. They wrote in Greek and lived in Egypt under Roman rule.

Mythology – Zosimos of Panopolis asserted that alchemy dated back to Pharaonic Egypt where it was the domain of the priestly class, though there is little to no evidence for his assertion.[31] Alchemical writers used Classical figures from Greek, Roman, and Egyptian mythology to illuminate their works and allegorize alchemical transmutation.[32] These included the pantheon of gods related to the Classical planets, Isis, Osiris, Jason, and many others.

The central figure in the mythology of alchemy is Hermes Trismegistus (or Thrice-Great Hermes). His name is derived from the god Thoth and his Greek counterpart Hermes. Hermes and his caduceus or serpent-staff, were among alchemy's principal symbols. According to Clement of Alexandria, he wrote what were called the "forty-two books of Hermes", covering all fields of knowledge.[33] The Hermetica of Thrice-Great Hermes is generally understood to form the basis for Western alchemical philosophy and practice, called the hermetic philosophy by its early practitioners. These writings were collected in the first centuries of the common era.

Technology – The dawn of Western alchemy is sometimes associated with that of metallurgy, extending back to 3500 BCE.[34] Many writings were lost when the emperor Diocletian ordered the burning of alchemical books[35] after suppressing a revolt in Alexandria (292 CE). Few original Egyptian documents on alchemy have survived, most notable among them the Stockholm papyrus and the Leyden papyrus X. Dating from 300 to 500 CE, they contained recipes for dyeing and making artificial gemstones, cleaning and fabricating pearls, and manufacturing of imitation gold and silver.[36] These writings lack the mystical, philosophical elements of alchemy, but do contain the works of Bolus of Mendes (or Pseudo-Democritus) which aligned these recipes with theoretical knowledge of astrology and the Classical elements.[37] Between the time of Bolus and Zosimos, the change took place that transformed this metallurgy into a Hermetic art.[38]

Philosophy – Alexandria acted as a melting pot for philosophies of Pythagoreanism, Platonism, Stoicism and Gnosticism which formed the origin of alchemy's character.[37] An important example of alchemy's roots in Greek philosophy, originated by Empedocles and developed by Aristotle, was that all things in the universe were formed from only four elements: earth, air, water, and fire. According to Aristotle, each element had a sphere to which it belonged and to which it would return if left undisturbed.[39] The four elements of the Greek were mostly qualitative aspects of matter, not quantitative, as our modern elements are; "...True alchemy never regarded earth, air, water, and fire as corporeal or chemical substances in the present-day sense of the word. The four elements are simply the primary, and most general, qualities by means of which the amorphous and purely quantitative substance of all bodies first reveals itself in differentiated form."[40] The Roman emperor Caligula is said "to have instituted experiments for producing gold out of orpiment (arsenic sulfide)." [41] Later alchemists extensively developed the mystical aspects of this concept. Alchemy coexisted alongside emerging Christianity. Lactantius believed Hermes Trismegistus had prophesied its birth. Augustine (354–430 CE) later affirmed this, but also condemned Trismegistus for idolatry.[42] Examples of Pagan, Christian, and Jewish alchemists can be found during this period.

Most of the Greco-Roman alchemists preceding Zosimos are known only by pseudonyms, such as Moses, Isis, Cleopatra, Democritus, and Ostanes. Others authors such as Komarios, and Chymes, we only know through fragments of text. After 400 CE, Greek alchemical writers occupied themselves solely in commenting on the works of these predecessors.[43] By the middle of the 7th century alchemy was almost an entirely mystical discipline.[44] It was at that time that Khalid Ibn Yazid sparked its migration from Alexandria to the Islamic world, facilitating the translation and preservation of Greek alchemical texts in the 8th and 9th centuries.[45]

The unicorn is a legendary animal that has been described since antiquity as a beast with a large, pointed, spiraling horn projecting from its forehead. The unicorn was depicted in ancient seals of the Indus Valley Civilization and was mentioned by the ancient Greeks in accounts of natural history by various writers, including Ctesias, Strabo, Pliny the Younger, and Aelian.[1] The Bible also describes an animal, the re'em, which some translations have erroneously rendered with the word unicorn.[1]

In European folklore, the unicorn is often depicted as a white horse-like or goat-like animal with a long horn and cloven hooves (sometimes a goat's beard). In the Middle Ages and Renaissance, it was commonly described as an extremely wild woodland creature, a symbol of purity and grace, which could only be captured by a virgin. In the encyclopedias its horn was said to have the power to render poisoned water potable and to heal sickness. In medieval and Renaissance times, the tusk of the narwhal was sometimes sold as unicorn horn.

nicorns are not found in Greek mythology, but rather in the accounts of natural history, for Greek writers of natural history were convinced of the reality of unicorns, which they located in India, a distant and fabulous realm for them. The earliest description is from Ctesias who, in his book Indika ("On India"), described them as wild asses, fleet of foot, having a horn a cubit and a half (700 mm, 27 inches) in length, and colored white, red and black.[2] Aristotle must be following Ctesias when he mentions two one-horned animals, the oryx (a kind of antelope) and the so-called "Indian ass".[3][4] Strabo says that in the Caucasus there were one-horned horses with stag-like heads.[5] Pliny the Elder mentions the oryx and an Indian ox (perhaps a rhinoceros) as one-horned beasts, as well as "a very fierce animal called the monoceros which has the head of the stag, the feet of the elephant, and the tail of the boar, while the rest of the body is like that of the horse; it makes a deep lowing noise, and has a single black horn, which projects from the middle of its forehead, two cubits (900 mm) in length."[6] In On the Nature of Animals (Περὶ Ζῴων Ἰδιότητος, De natura animalium), Aelian, quoting Ctesias, adds that India produces also a one-horned horse (iii. 41; iv. 52),[7][8] and says (xvi. 20)[9] that the monoceros (Greek: μονόκερως) was sometimes called cartazonos (Greek: καρτάζωνος), which may be a form of the Arabic karkadann, meaning "rhinoceros".

Cosmas Indicopleustes, a merchant of Alexandria who lived in the 6th century, made a voyage to India and subsequently wrote works on cosmography. He gives a description of a unicorn based on four brass figures in the palace of the King of Ethiopia. He states, from report, that "it is impossible to take this ferocious beast alive; and that all its strength lies in its horn. When it finds itself pursued and in danger of capture, it throws itself from a precipice, and turns so aptly in falling, that it receives all the shock upon the horn, and so escapes safe and sound."[10][11]

A one-horned animal (which may be just a bull in profile) is found on some seals from the Indus Valley Civilization.[12] Seals with such a design are thought to be a mark of high social rank.[13]

Middle Ages and Renaissance
Youths riding goats (a Dionysiac motif in antiquity) on 12th-century capitals from the abbey of Mozac in the Auvergne. The goats are indistinguishable from unicorns.
Virgin Mary holding the unicorn (c. 1480), detail of the Annunciation with the Unicorn Polyptych, National Museum, Warsaw
Wild woman with unicorn, c. 1500–1510 (Basel Historical Museum)

Medieval knowledge of the fabulous beast stemmed from biblical and ancient sources, and the creature was variously represented as a kind of wild ass, goat, or horse.

The predecessor of the medieval bestiary, compiled in Late Antiquity and known as Physiologus (Φυσιολόγος), popularized an elaborate allegory in which a unicorn, trapped by a maiden (representing the Virgin Mary), stood for the Incarnation. As soon as the unicorn sees her, it lays its head on her lap and falls asleep. This became a basic emblematic tag that underlies medieval notions of the unicorn, justifying its appearance in every form of religious art. Interpretations of the unicorn myth focus on the medieval lore of beguiled lovers,[citation needed] whereas some religious writers interpret the unicorn and its death as the Passion of Christ. The myths refer to a beast with one horn that can only be tamed by a virgin; subsequently, some writers translated this into an allegory for Christ's relationship with the Virgin Mary.

The unicorn also figured in courtly terms: for some 13th century French authors such as Thibaut of Champagne and Richard de Fournival, the lover is attracted to his lady as the unicorn is to the virgin. With the rise of humanism, the unicorn also acquired more orthodox secular meanings, emblematic of chaste love and faithful marriage. It plays this role in Petrarch's Triumph of Chastity, and on the reverse of Piero della Francesca's portrait of Battista Strozzi, paired with that of her husband Federico da Montefeltro (painted c 1472-74), Bianca's triumphal car is drawn by a pair of unicorns.[14]

he Throne Chair of Denmark is made of "unicorn horns" – almost certainly narwhal tusks. The same material was used for ceremonial cups because the unicorn's horn continued to be believed to neutralize poison, following classical authors.

The unicorn, tamable only by a virgin woman, was well established in medieval lore by the time Marco Polo described them as "scarcely smaller than elephants. They have the hair of a buffalo and feet like an elephant's. They have a single large black horn in the middle of the forehead... They have a head like a wild boar's… They spend their time by preference wallowing in mud and slime. They are very ugly brutes to look at. They are not at all such as we describe them when we relate that they let themselves be captured by virgins, but clean contrary to our notions." It is clear that Marco Polo was describing a rhinoceros.[citation needed] In German, since the 16th century, Einhorn ("one-horn") has become a descriptor of the various species of rhinoceros.

The horn itself and the substance it was made of was called alicorn, and it was believed that the horn holds magical and medicinal properties. The Danish physician Ole Worm determined in 1638 that the alleged alicorns were the tusks of narwhals.[15] Such beliefs were examined wittily and at length in 1646 by Sir Thomas Browne in his Pseudodoxia Epidemica.[16]

False alicorn powder, made from the tusks of narwhals or horns of various animals, has been sold in Europe for medicinal purposes as late as 1741.[17] The alicorn was thought to cure many diseases and have the ability to detect poisons, and many physicians would make "cures" and sell them. Cups were made from alicorn for kings and given as a gift; these were usually made of ivory or walrus ivory. Entire horns were very precious in the Middle Ages and were often really the tusks of narwhals.[18]

The qilin (Chinese: 麒麟), a creature in Chinese mythology, is sometimes called "the Chinese unicorn", and some ancient accounts describe a single horn as its defining feature. However, it is more accurately described as a hybrid animal that looks less unicorn than chimera, with the body of a deer, the head of a lion, green scales and a long forwardly-curved horn. The Japanese version (kirin) more closely resembles the Western unicorn, even though it is based on the Chinese qilin. The Quẻ Ly of Vietnamese myth, similarly sometimes mistranslated "unicorn" is a symbol of wealth and prosperity that made its first appearance during the Duong Dynasty, about 600 CE, to Emperor Duong Cao To, after a military victory which resulted in his conquest of Tây Nguyên. In November 2012 the History Institute of the DPRK Academy of Social Sciences, as well as the Korea News Service, reported that the Kiringul had been found, which is associated with a kirin ridden by King Dongmyeong of Goguryeo.[38][39]

Beginning in the Ming Dynasty, the qilin became associated with giraffes, after Zheng He's voyage to East Africa brought a pair of the long-necked animals and introduced them at court in Nanjing as qilin.[40] The resemblance to the qilin was noted in the giraffe's ossicones (bony protrusions from the skull resembling horns), graceful movements, and peaceful demeanor.[41]

A dragon is a legendary creature, typically with serpentine or reptilian traits, that features in the myths of many cultures. There are two distinct cultural traditions of dragons: the European dragon, derived from European folk traditions and ultimately related to Greek and Middle Eastern mythologies, and the Chinese dragon, with counterparts in Japan (namely the Japanese dragon), Korea and other East Asian countries.[1]

The two traditions may have evolved separately, but have influenced each other to a certain extent, particularly with the cross-cultural contact of recent centuries. The English word "dragon" derives from Greek δράκων (drákōn), "dragon, serpent of huge size, water-snake".[2]

The association of the serpent with a monstrous opponent overcome by a heroic deity has its roots in the mythology of the Ancient Near East, including Canaanite (Hebrew, Ugaritic), Hittite and Mesopotamian. Humbaba, the fire-breathing dragon-fanged beast first described in the Epic of Gilgamesh is sometimes described as a dragon with Gilgamesh playing the part of dragon-slayer. The legless serpent (Chaoskampf) motif entered Greek mythology and ultimately Christian mythology, although the serpent motif may already be part of prehistoric Indo-European mythology as well, based on comparative evidence of Indic and Germanic material.

Although dragons occur in many legends around the world, different cultures have varying stories about monsters that have been grouped together under the dragon label. Some dragons are said to breathe fire or to be poisonous, such as in the Old English poem Beowulf.[3] (Dr. Paweł Frelik, one-time Editor-in-Chief of the European Journal of American Studies and President of the Science Fiction Research Association (2013-2014), writes, "Dragons emitting fire were traditional elements of folk tales and myths and, as such, later permeated into modern fantasy. They are present, for example, in Anne McCaffrey's Dragonflight and its sequels."[4]) They are commonly portrayed as serpentine or reptilian, hatching from eggs and possessing typically scaly or feathered bodies. They are sometimes portrayed as hoarding treasure. Some myths portray them with a row of dorsal spines. European dragons are more often winged, while Chinese dragons resemble large snakes. Dragons can have a variable number of legs: none, two, four, or more when it comes to early European literature.

Dragons are often held to have major spiritual significance in various religions and cultures around the world. In many Asian cultures dragons were, and in some cultures still are, revered as representative of the primal forces of nature, religion and the universe. They are associated with wisdom—often said to be wiser than humans—and longevity. They are commonly said to possess some form of magic or other supernatural power, and are often associated with wells, rain, and rivers. In some cultures, they are also said to be capable of human speech. In some traditions dragons are said to have taught humans to talk.

European dragons exist in folklore and mythology among the overlapping cultures of Europe. Dragons are generally depicted as living in rivers or having an underground lair or cave.[9] They are commonly described as having hard or armoured hide, and are rarely described as flying, despite often being depicted with wings.

In China, depiction of the dragon (traditional:龍;simplified:龙) can be found in artifacts from the Shang and Zhou dynasties with examples dating back to the 16th century BC.[20] Archaeologist Zhōu Chong-Fa believes that the Chinese word for dragon is an onomatopoeia of the sound of thunder.[21] The Chinese name for dragon is pronounced lóng in Mandarin Chinese[20] or lùhng in Cantonese.[22] Sometime after the 9th century AD, Japan adopted the Chinese dragon through the spread of Buddhism.[20]

The Chinese dragon is the highest-ranking animal in the Chinese animal hierarchy, strongly associated at one time with the emperor and hence power and majesty (the mythical bird fenghuang was the symbol of the Chinese empress), still recognized and revered. Its origins are vague, but its "ancestors can be found on Neolithic pottery as well as Bronze Age ritual vessels."[23] Tradition has it composed of nine different animals, with nine sons, each with its own imagery and affiliations. It is the only mythological animal of the 12 animals that represent the Chinese calendar. 2012 was the Chinese year of the Water Dragon.

Japanese dragon myths amalgamate native legends with imported stories about dragons from China, Korea and India. Like these other Asian dragons, most Japanese ones are water deities associated with rainfall and bodies of water, and are typically depicted as large, wingless, serpentine creatures with clawed feet. Gould writes (1896:248),[24] the Japanese dragon is "invariably figured as possessing three claws".

European dragons are legendary creatures in folklore and mythology among the overlapping cultures of Europe.[1]

In the modern period, the European dragon is typically depicted as a huge, fire-breathing, scaly, horned, lizard-like creature; the creature also has leathery, bat-like wings, four legs, and a long, muscular prehensile tail. Some depictions show dragons with feathered wings, crests, fiery manes, ivory spikes running down its spine, and various exotic decorations.

In folktales, dragon's blood often contains magical properties. For example, in the opera Siegfried, dragon's blood allows Siegfried to understand the language of the Forest Bird. The typical dragon protects a cavern or castle filled with gold and treasure and is often associated with a great hero who tries to slay it.

Though a winged creature, the dragon is generally to be found in its underground lair, a cave that identifies it as an ancient creature of earth. Possibly, the dragons of European and Mid-Eastern mythology stem from the cult of snakes found in religions throughout the world.

Dragons are usually shown in modern times with a body like a huge lizard, or a snake with two pairs of lizard-type legs, and able to emit fire from their mouths. This is commonly referred to as a Fire-Breathing Dragon. The European dragon has bat-like wings growing from its back. A dragon-like creature with wings but only a single pair of legs is known as a wyvern. The European dragon are most associated with fire breathing.

It has been speculated that accounts of spitting cobras may be the origin of the myths of fire-breathing dragons.[5]

In Western folklore, dragons are usually portrayed as evil, with the exceptions mainly in Welsh folklore and modern fiction. This is in contrast to Asian dragons, who are traditionally depicted as more benevolent creatures. In the modern period, the European dragon is typically depicted as a huge fire-breathing, scaly and horned lizard-like creature, with (leathery, bat-like) wings, with four legs and a long muscular tail. It is sometimes shown with feathered wings, crests, fiery manes, ivory spikes running down its spine and various exotic colorations. Dragon's blood often has magical properties; for example, in the opera Siegfried it let Siegfried understand the language of the Forest Bird. The typical dragon protects a cavern or castle filled with gold and treasure and is often associated with a great hero who tries to slay it. Though a winged creature, the dragon is generally to be found in its underground lair, a cave that identifies it as an ancient creature of earth. Possibly, the dragons of European and Mid-Eastern mythology stem from the cult of snakes found in religions throughout the world.

Many European stories of dragons have them guarding a treasure hoard. Both Fafnir and Beowulf's dragon guarded earthen mounds full of ancient treasure. The treasure was cursed and brought ill to those who later possessed it.

Notwithstanding their folkloric associations, there is no etymological connection between dragons and the ghoulish figures known as draugar in Old Norse, who haunt rich burial mounds.

The poem Beowulf describes a draca (dragon) also as wyrm (worm, or serpent) and its movements by the Anglo-Saxon verb bugan, "to bend", and says that it has a venomous bite; all of these indicate a snake-like form and movement rather than with a lizard-like or dinosaur-like body as in later belief (though the dragon of Beowulf does show several features that would later become popularized with dragons–namely, it breathes fire–lives underground, and collects treasure).

Like most dragons, the Catalan dragon (Catalan drac) is an enormous serpent with two or, rarely, four legs and sometimes a pair of wings. As in many other parts of the world, the dragon's face may be like that of some other animal, such as a lion or bull. As is common elsewhere, Catalan dragons are fire-breathers, and the dragon-fire is all-consuming. Catalan dragons also can emit a fetid odor, which can rot away anything it touches.

A  grimoire is a textbook of magic. Such books typically include instructions on how to create magical objects like talismans and amulets, how to perform magical spells, charms and divination and also how to summon or invoke supernatural entities such as angels, spirits, and demons.[1] In this manner while all books on magic could be thought of as grimoires, not all magical books should.[2]

The scientific method is a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge.[2] To be termed scientific, a method of inquiry is commonly based on empirical or measurable evidence subject to specific principles of reasoning.[3] The Oxford English Dictionary defines the scientific method as "a method or procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses."[4]

The scientific method is an ongoing process, which usually begins with observations about the natural world. Human beings are naturally inquisitive, so they often come up with questions about things they see or hear and often develop ideas (hypotheses) about why things are the way they are. The best hypotheses lead to predictions that can be tested in various ways, including making further observations about nature. In general, the strongest tests of hypotheses come from carefully controlled and replicated experiments that gather empirical data. Depending on how well the tests match the predictions, the original hypothesis may require refinement, alteration, expansion or even rejection. If a particular hypothesis becomes very well supported a general theory may be developed.[1]

Although procedures vary from one field of inquiry to another, identifiable features are frequently shared in common between them. The overall process of the scientific method involves making conjectures (hypotheses), deriving predictions from them as logical consequences, and then carrying out experiments based on those predictions.[5][6] A hypothesis is a conjecture, based on knowledge obtained while formulating the question. The hypothesis might be very specific or it might be broad. Scientists then test hypotheses by conducting experiments. Under modern interpretations, a scientific hypothesis must be falsifiable, implying that it is possible to identify a possible outcome of an experiment that conflicts with predictions deduced from the hypothesis; otherwise, the hypothesis cannot be meaningfully tested.[7]

The purpose of an experiment is to determine whether observations agree with or conflict with the predictions derived from a hypothesis.[8] Experiments can take place in a college lab, on a kitchen table, at CERN's Large Hadron Collider, at the bottom of an ocean, on Mars, and so on. There are difficulties in a formulaic statement of method, however. Though the scientific method is often presented as a fixed sequence of steps, it represents rather a set of general principles.[9] Not all steps take place in every scientific inquiry (or to the same degree), and are not always in the same order.[10]

In ecology, predation is a biological interaction where a predator (an organism that is hunting) feeds on its prey (the organism that is attacked).[1] Predators may or may not kill their prey prior to feeding on them, but the act of predation often results in the death of its prey and the eventual absorption of the prey's tissue through consumption.[2] Thus predation is often, though not always, carnivory. Other categories of consumption are herbivory (eating parts of plants), mycophagy (eating parts of fungi) and detritivory, the consumption of dead organic material (detritus). All these consumption categories fall under the rubric of consumer-resource systems.[3] It can often be difficult to separate various types of feeding behaviors.[1] For example, some parasitic species prey on a host organism and then lay their eggs on it for their offspring to feed on it while it continues to live in or on its decaying corpse after it has died. The key characteristic of predation however is the predator's direct impact on the prey population. On the other hand, detritivores simply eat dead organic material arising from the decay of dead individuals and have no direct impact on the "donor" organism(s).

Selective pressures imposed on one another often leads to an evolutionary arms race between prey and predator, resulting in various antipredator adaptations. Ways of classifying predation surveyed here include grouping by trophic level or diet, by specialization, and by the nature of the predator's interaction with prey.

Biological interactions are the effects that the organisms in a community have on one another. In the natural world no organism exists in absolute isolation, and thus every organism must interact with the environment and other organisms. An organism's interactions with its environment are fundamental to the survival of that organism and the functioning of the ecosystem as a whole.[1]
The black walnut secretes a chemical from its roots that harms neighboring plants, an example of antagonism.
The mutualism interaction between the red-billed oxpecker and the giraffe.[2]

In ecology, biological interactions can involve individuals of the same species (intraspecific interactions) or individuals of different species (interspecific interactions). These can be further classified by either the mechanism of the interaction or the strength, duration and direction of their effects.[3] Species may interact once in a generation (e.g. pollination) or live completely within another (e.g. endosymbiosis). Effects range from consumption of another individual (predation, herbivory, or cannibalism), to mutual benefit (mutualism). Interactions need not be direct; individuals may affect each other indirectly through intermediaries such as shared resources or common enemies.

erms that explicitly indicate the quality of benefit or harm in terms of fitness experienced by participants in an interaction are listed in the chart. There are six possible combinations, ranging from mutually beneficial through neutral to mutually harmful interactions. The level of benefit or harm is continuous and not discrete, so a particular interaction may have a range from trivially harmful through to deadly, for example. It is important to note that these interactions are not always static. In many cases, two species will interact differently under different conditions. This is particularly true in, but not limited to, cases where species have multiple, drastically different life stages.
Competition
Main article: Natural selection § Competition

Competition is a mutually detrimental interaction between individuals, populations or species, but rarely between clades.[4]
Amensalism

Amensalism is an interaction where an organism inflicts harm to another organism without any costs or benefits received by the other.[5] A clear case of amensalism is where sheep or cattle trample grass. Whilst the presence of the grass causes negligible detrimental effects to the animal's hoof, the grass suffers from being crushed. Amensalism is often used to describe strongly asymmetrical competitive interactions, such as has been observed between the Spanish ibex and weevils of the genus Timarcha which feed upon the same type of shrub. Whilst the presence of the weevil has almost no influence on food availability, the presence of ibex has an enormous detrimental effect on weevil numbers, as they consume significant quantities of plant matter and incidentally ingest the weevils upon it.[6]

This is not a bee, but a syrphid fly, a Batesian mimic.
Further information: Predation, parasitism, herbivory, Batesian mimicry

In antagonistic interactions, one species benefits at the expense of another. Predation is an interaction between organisms in which one organism captures biomass from another. It is often used as a synonym for carnivory but in its widest definition includes all forms of one organism eating another, regardless of trophic level (e.g., herbivory), closeness of association (e.g., parasitism and parasitoidism) and harm done to prey (e.g., grazing). Intraguild predation occurs when an organism preys upon another of different species but at the same trophic level (e.g., coyotes kill and ingest gray foxes in southern California). Batesian mimicry is also an antagonistic interaction, where one species has evolved to mimic another, to the advantage of the copying species but to the detriment of the species being mimicked.
Neutralism

Neutralism describes the relationship between two species that interact but do not affect each other. It describes interactions where the health of one species has absolutely no effect whatsoever on that of the other. Examples of true neutralism are virtually impossible to prove and most ecologists (as well as textbooks) would agree that this concept does not exist.[7] When dealing with the complex networks of interactions presented by ecosystems, one cannot assert positively that there is absolutely no competition between or benefit to either species. However, the term is often used to describe situations where interactions are negligible or insignificant.

Synnecrosis is a particular case in which the interaction is so mutually detrimental that it results in death, as in the case of some parasitic relationships.[citation needed] It is a rare and necessarily short-lived condition as evolution selects against it. The term is seldom used.

The following two interactions can be classed as facilitative. Facilitation describes species interactions that benefit at least one of the participants and cause no harm to either.[9] Facilitations can be categorized as mutualisms, in which both species benefit, or commensalisms, in which one species benefits and the other is unaffected. Much of classic ecological theory (e.g., natural selection, niche separation, metapopulation dynamics) has focused on negative interactions such as predation and competition, but positive interactions (facilitation) are receiving increasing focus in ecological research.[9][10][11][12][13]
Commensalism
Main article: Commensalism

Commensalism benefits one organism and the other organism is neither benefited nor harmed. It occurs when one organism takes benefits by interacting with another organism by which the host organism is not affected. A good example is a remora living with a shark. Remoras eat leftover food from the shark. The shark is not affected in the process, as remoras eat only leftover food of the shark, which does not deplete the shark's resources.

Pollination illustrates mutualism between flowering plants and their animal pollinators.

Mutualism is an interaction between two or more species, where species derive a mutual benefit, for example an increased carrying capacity. Similar interactions within a species are known as co-operation. Mutualism may be classified in terms of the closeness of association, the closest being symbiosis, which is often confused with mutualism. One or both species involved in the interaction may be obligate, meaning they cannot survive in the short or long term without the other species. Though mutualism has historically received less attention than other interactions such as predation,[14] it is very important subject in ecology. Examples include cleaner fish, pollination and seed dispersal, gut flora, Müllerian mimicry and nitrogen fixation by bacteria in the root nodules of legumes.

Combustion burning is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion in a fire produces a flame, and the heat produced can make combustion self-sustaining. Combustion is often a complicated sequence of elementary radical reactions. Solid fuels, such as wood, first undergo endothermic pyrolysis to produce gaseous fuels whose combustion then supplies the heat required to produce more of them. Combustion is often hot enough that light in the form of either glowing or a flame is produced. A simple example can be seen in the combustion of hydrogen and oxygen into water vapor, a reaction commonly used to fuel rocket engines. This reaction releases enthalpy (heat).

Uncatalyzed combustion in air requires fairly high temperatures. Complete combustion is stoichiometric with respect to the fuel, where there is no remaining fuel, and ideally, no remaining oxidant. Thermodynamically, the chemical equilibrium of combustion in air is overwhelmingly on the side of the products. However, complete combustion is almost impossible to achieve, since the chemical equilibrium is not necessarily reached, or may contain unburnt products such as carbon monoxide, hydrogen and even carbon (soot or ash). Thus, the produced smoke is usually toxic and contains unburned or partially oxidized products. Any combustion at high temperatures in atmospheric air, which is 78 percent nitrogen, will also create small amounts of several nitrogen oxides, commonly referred to as NO
x, since the combustion of nitrogen is thermodynamically favored at high, but not low temperatures. Since combustion is rarely clean, flue gas cleaning or catalytic converters may be required by law.

Fires occur naturally, ignited by lightning strikes or by volcanic products. Combustion (fire) was the first controlled chemical reaction discovered by humans, in the form of campfires and bonfires, and continues to be the main method to produce energy for humanity. Usually, the fuel is carbon, hydrocarbons or more complicated mixtures such as wood that contains partially oxidized hydrocarbons. The thermal energy produced from combustion of either fossil fuels such as coal or oil, or from renewable fuels such as firewood, is harvested for diverse uses such as cooking, production of electricity or industrial or domestic heating. Combustion is also currently the only reaction used to power rockets. Combustion is also used to destroy (incinerate) waste, both nonhazardous and hazardous.

Oxidants for combustion have high oxidation potential and include atmospheric or pure oxygen, chlorine, fluorine, chlorine trifluoride, nitrous oxide and nitric acid. For instance, hydrogen burns in chlorine to form hydrogen chloride with the liberation of heat and light characteristic of combustion. Although usually not catalyzed, combustion can be catalyzed by platinum or vanadium, as in the contact process.

A wyvern, sometimes spelled wivern, is a legendary winged creature with a dragon's head and wings; a reptilian body; two legs; and a barbed tail. A sea-dwelling variant, dubbed the sea-wyvern, has a fish tail in place of a barbed dragon's tail.

The wyvern in its various forms is important to heraldry, frequently appearing as a mascot of schools and athletic teams (chiefly in the United States and United Kingdom). It is a popular creature in European and British literature, video games, and modern fantasy. The wyvern is often (but not always) associated with cold weather and ice, and it will sometimes possess a venomous bite and rarely have the ability to breathe fire.

The wyvern has often been confused with the dragon (even though the two are distinct, unrelated creatures), due to the similarities between them and due to the wyvern being a lesser-known mythical creature. In the middle ages, no clear distinction was made between the two. Since the sixteenth century, in English, Scottish, and Irish heraldry, the key distinction has been that a wyvern has two legs, whereas a dragon has four; however, this distinction is not generally observed in the heraldry of other European countries, where two-legged dragons are entirely acceptable.[3]

In the fantasy genre, the wyvern is usually considered to have two legs, whereas the dragon may have either four or none. The wyvern is regarded, moreover, as the distant, lesser cousin to the dragon, similar to a dog being the distant cousin to the wolf. Wyverns tend to be smaller, weaker, not as intelligent, and ultimately inferior to the much more ferocious and powerful dragon. While a dragon almost always has the ability to breathe fire (though other types of breath such as lightning have been seen as well), a wyvern will usually be unable to breathe fire. Those that can breathe fire are sometimes termed "fire drakes" and are still considered a lesser form. A wyvern will typically be unable to speak, while a dragon often does have that ability.[4]

Ice is water, frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color.

In the Solar System, ice occurs naturally from as close to the Sun as Mercury to as far as the Oort cloud. Beyond the Solar System, it occurs as interstellar ice. It is abundant on Earth's surface – particularly in the polar regions and above the snow line[1] – and, as a common form of precipitation and deposition, plays a key role in Earth's water cycle and climate. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes.

Ice molecules exhibit different phases (packing geometries) that depend on temperature and pressure. Virtually all the ice on Earth's surface and in its atmosphere is of a hexagonal crystalline structure denoted as ice. The most common phase transition to ice Ih occurs when liquid water is cooled at standard atmospheric pressure. It may also be deposited directly by water vapor, as happens in the formation of frost. The transition from ice to water is melting and from ice directly to water vapor is sublimation.

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy.[1] Weather, seen from an anthropological perspective, is something all humans in the world constantly experience through their senses, at least while being outside. There are socially and scientifically constructed understandings of what weather is, what makes it change, the effect it has on humans in different situations, etc.[2] Therefore, weather is something people often communicate about.

Most weather phenomena occur in the troposphere,[3][4] just below the stratosphere. Weather generally refers to day-to-day temperature and precipitation activity, whereas climate is the term for the statistics of atmospheric conditions over longer periods of time.[5] When used without qualification, "weather" is generally understood to mean the weather of Earth.

Weather is driven by air pressure (temperature and moisture) differences between one place and another. These pressure and temperature differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. The strong temperature contrast between polar and tropical air gives rise to the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. On Earth's surface, temperatures usually vary annually. Over thousands of years, changes in Earth's orbit can affect the amount and distribution of solar energy received by the Earth, thus influencing long-term climate and global climate change.

Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes due to differences in compressional heating. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The system is a chaotic system; so small changes to one part of the system can grow to have large effects on the system as a whole. Human attempts to control the weather have occurred throughout human history, and there is evidence that human activities such as agriculture and industry have modified weather patterns.

Studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies. A star's corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind.

An experiment is an orderly procedure carried out with the goal of verifying, refuting, or establishing the validity of a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results. There also exist natural experimental studies.

A child may carry out basic experiments to understand the nature of gravity, while teams of scientists may take years of systematic investigation to advance the understanding of a phenomenon. Experiments and other types of hands-on activities are very important to student learning in the science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning, especially when used over time.[1] Experiments can vary from personal and informal natural comparisons (e.g. tasting a range of chocolates to find a favorite), to highly controlled (e.g. tests requiring complex apparatus overseen by many scientists that hope to discover information about subatomic particles). Uses of experiments vary considerably between the natural and human sciences.

Experiments typically include controls, which are designed to minimize the effects of variables other than the single independent variable. This increases the reliability of the results, often through a comparison between control measurments and the other measurements. Scientific controls are a part of the scientific method. Ideally, all variables in an experiment will be controlled (accounted for by the control measurements) and none will be uncontrolled. In such an experiment, if all the controls work as expected, it is possible to conclude that the experiment is working as intended and that the results of the experiment are due to the effect of the variable being tested.

In the centre of this shield, which was covered with dragon's scales, bordered with serpents, and which she sometimes wore as a breastplate, was the awe-inspiring head of the Medusa, which had the effect of turning to stone all beholders.

Sometimes she appears seated in a chariot drawn by winged dragons, at others she stands erect, her figure drawn up to its full height, and always fully draped.

This spring was situated in a wood and guarded by a fierce dragon.

She commanded him to sow the teeth of the dead dragon in the ground.

He carefully guarded the entrance to the grove by placing before it an immense dragon, which never slept.

Then I saw the horses we were on had changed to unicorns, and they began trampling the grapes and breaking them.

There is the Unicorn with the one horn, and what is it he is going against?

We are very few now, but the army of the Unicorns will be a great army!

Aerodynamics, from Greek ἀήρ aer (air) + δυναμική (dynamics), is a branch of Fluid dynamics concerned with studying the motion of air, particularly when it interacts with a solid object, such as an airplane wing. Aerodynamics is a sub-field of fluid dynamics and gas dynamics, and many aspects of aerodynamics theory are common to these fields. The term aerodynamics is often used synonymously with gas dynamics, with the difference being that "gas dynamics" applies to the study of the motion of all gases, not limited to air.

Formal aerodynamics study in the modern sense began in the eighteenth century, although observations of fundamental concepts such as aerodynamic drag have been recorded much earlier. Most of the early efforts in aerodynamics worked towards achieving heavier-than-air flight, which was first demonstrated by Wilbur and Orville Wright in 1903. Since then, the use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer simulations has formed the scientific basis for ongoing developments in heavier-than-air flight and a number of other technologies. Recent work in aerodynamics has focused on issues related to compressible flow, turbulence, and boundary layers, and has become increasingly computational in nature.

A vortex is created by the passage of an aircraft wing, revealed by smoke. Vortices are one of the many phenomena associated with the study of aerodynamics.
As aircraft speed increased, designers began to encounter challenges associated with air compressibility at speeds near or greater than the speed of sound. The differences in air flows under these conditions led to problems in aircraft control, increased drag due to shock waves, and structural dangers due to aeroelastic flutter.

By the time the sound barrier was broken, much of the subsonic and low supersonic aerodynamics knowledge had matured. The Cold War fueled an ever evolving line of high performance aircraft. Computational fluid dynamics began as an effort to solve for flow properties around complex objects and has rapidly grown to the point where entire aircraft can be designed using a computer, with wind-tunnel tests followed by flight tests to confirm the computer predictions. Knowledge of supersonic and hypersonic aerodynamics has also matured since the 1960s, and the goals of aerodynamicists have shifted from understanding the behavior of fluid flow to understanding how to engineer a vehicle to interact appropriately with the fluid flow.

A unicorn horn, also known as an alicorn,[1] is a legendary object whose reality may have been accepted in Western Europe throughout the Middle Ages. Many healing powers and antidote's virtues were attributed to the horn of the unicorn. These properties, assumed real since the 13th century, made it one of the most expensive and most reputable remedies during the Renaissance,[2] and justified its use in royal courts. Beliefs related to the "unicorn horn" influenced alchemy through spagyric medicine. The horn's purification properties were eventually put to the test in, for example, the book of Ambroise Paré, Discourse on unicorn - marking the beginnings of the experimental method.

Seen as one of the most valuable assets that a king could possess, unicorn horns were exchanged and could be purchased at apothecaries as universal antidotes until the 18th century. Other horns were displayed in cabinets of curiosities. The horn was used to create sceptres and other royal objects, such as the "unicorn throne" of the Danish kings, the sceptre and imperial crown of the Austrian Empire, and the scabbard and the hilt of the sword of Charles the Bold. The legendary unicorn was never captured, but its symbolic association with virginity made it the symbol of the incarnation of God's Word, innocence and divine power

Belief in the power of the unicorn's horn and its origins persisted from the Middle Ages to the 18th century, when the true source, the narwhal, was discovered. This marine mammal is the true bearer of the "unicorn horn", actually an extended tooth found in the mouth of males and some females. Since then, the unicorn horn has been mentioned in fantasy works, role-playing games and video games, which make use of its legendary symbolism.

Coming from an ancient figure, the unicorn was described by Ctesias as carrying a horn which Indian princes would use to make hanaps against poison. These writings were taken up by Aristotle and Pliny the Elder;[3] Claudius Aelianus also said that drinking in this horn protects against diseases and poisons.[4] These writings influenced the authors from the Middle Ages to the Renaissance: the unicorn becomes the most important and most frequently mentioned imaginary animal in the West, its existence was considered real. Other parts of its body were given medicinal properties and, in the 12th century, abbess Hildegard of Bingen recommended an ointment against leprosy made from foie de licorne and egg yolk.[5] Wearing a unicorn leather belt was supposed to protect a person from the plague and fever, while leather shoes of this animal lure diseases away from feet.[6]

The actual medicinal use was linked to its horn and purification power assumed true since the Antiquity, which was explicitly mentioned for the first time in the 13th century. Legends about this properties circulating since the Middle Ages were are the origin of a flourishing trade of these objects, which became more common up to the late 18th century, when their true origin was unknown. The unicorn never existed as represented, it is most often narwhal teeth known as "unicorn horns" during these times.[7]

The first reference to the cleansing power of the unicorn appears in an interpretation of the Physiologus (dated 14th century), when reference is made to a large lake where animals congregate to drink:

    But before they are gathered, the snake comes and throws his poison in the water. So many animals notice the poison and dare not to drink, and they expect the unicorn. It comes and it goes immediately to the lake, with its horn making the sign of the cross, it makes the poison harmless. All other animals drink then.[8]

The theme soon became popular, the stage of purification of water by a unicorn is taken in 1389 by the father Johann van Hesse, who claims to have seen a unicorn emerge from the sea to clean impure water so that animals could drink[9] Symbolically, the snake that poisons the water is the devil and the unicorn represent Christ the Redeemer.[10] The origin of this legend seems Indian, through the Greek texts mention the fact that the Indian nobles might drink out of unicorn horns to protect themselves from diseases and poisons.[9]

The unicorn is most often represented by a river, a lake or a fountain, while animals wait for her to finish her work to drink. This scene is very common in the art of the 16th and 17th centuries.[11] Studies and translations of these drawings and stories popularized the belief that the power of the animal comes from its horn, which would eliminate the poisons as it hits a liquid.[9] Water purification forge the legend on the properties of the "unicorn horn" and later justifies its use as a universal antidote.

The properties of the unicorn horn can be paralleled to those of the bezoar stone, another object of animal origin known in the Renaissance medicine and exposed as a rarity in the cabinets of curiosities.[12]

The unicorn horn was very quickly assigned many medicinal properties and, over time, in addition to the purification of polluted water in nature,[13] its use was recommended against rubella, measles, fevers and pains.[14] The monks of the Parisians monasteries used to soak it in the drinking water given to lepers.[13] It acted as an antidote and, in a powder form, was known to facilitate wound healing, help neutralize poisons (such as scorpion or viper venom)[15] or against the plague.[16] It would also have an aphrodisiac power known since ancient times[17] and would test the virginity of young girls.[18] The horn was consumed in several ways, in substance or infusion[19]

Its prophylactic function and magical power, although known for centuries, while its trade increases, several «fake» horns and false powders appeared.[20] The astronomical value achieved by these objects left to assume that their imaginary virtues could cause real healing,[13] probably due to the placebo effect.

This use of the unicorn horn in medicine is due to the fact that therapists then have very few instruments and objects, and the ancient heritage meant that they were only instruments of God. The Inquisition played a role in this belief: to doubt the powers of the horn meant doubting the existence of the unicorn itself, animal of God mentioned in a translation of the Bible. Skeptics risked to be burned at the stake.[21]

Many works are devoted to the explanation and defense of the medicinal properties of the «unicorn horn», including The Treaty of the Unicorn, its wonderful properties and its use (1573) by Andrea Bacci and Natural History, Hunting, Virtues, and Use of Lycorn (1624) by apothecary Laurent Catelan. Bacci probably wrote his book at the request of his patients, who were major investors in the unicorn horn trade.[22]

Twisted shape "unicorn horns" were exchanged and in circulation for a long time: according to a legend, the "horn" on display at the Musée national du Moyen Âge was a gift from the Caliph of Baghdad, Harun al-Rashid, to Charlemagne in 807.[4] It measures almost three meters.[23] An eight-foot long horn is exposed in Bruges, Flanders.[4] Since the Middle Ages, the "unicorn horn" is supposed to be the most valuable asset that a king could possess.[15] Its medicinal use is attested since the 13th century, when pharmacists incorporated narwhal teeth (presented as unicorn horns) in their treatments and they had large pieces so it could not be confused with that of another animal, such as ox.[24] These objects would have been exchanged up to eleven times their weight in gold.[13] Some horns, introduced reportedly during the Fourth Crusade of Constantinople, were thrown into the pit of the Doge's Palace in Venice, so that water could never be poisoned. Horns considered sacred relics can be found at the Council of Trent in 1563, as well as the Saint-Denis Cathedral in Paris, St Mark's Basilica in Venice and Westminster Abbey in London. They were usually mounted on silver socles and presented as trophies that could only be shown for important ceremonies.[15]

Ambroise Paré explains that the horns were used in the court of the King of France to detect the presence of poison in food and drink: if the horn became hot and started to smoke, then the dish was poisoned.[25] Pope Clement VII would have offered a unicorn horn of two cubits long to King Francis I of France at the wedding of his niece Catherine de' Medici in Marseille in October 1533,[26] and the king did not ever move without a bag filled with unicorn powder.[3] Also, the Grand Inquisitor Torquemada always bore his unicorn horn to protect himself from poison and murderers.[27]

A winged unicorn is a fictional horse with wings and the horn of a unicorn.

Medicine is the science and practice of the diagnosis, treatment, and prevention of disease.[1][2] The word medicine is derived from the Latin ars medicina, meaning the art of healing.[3][4] Medicine encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness.

Contemporary medicine applies biomedical sciences, biomedical research, genetics and medical technology to diagnose, treat, and prevent injury and disease, typically through pharmaceuticals or surgery, but also through therapies as diverse as psychotherapy, external splints and traction, prostheses, biologics, and ionizing radiation, amongst others.[5]

Medicine has existed for thousands of years, during most of which it was an art (an area of skill and knowledge) frequently having connections to the religious and philosophical beliefs of local culture. For example, a medicine man would apply herbs and say prayers for healing, or an ancient philosopher and physician would apply bloodletting according to the theories of humorism. In recent centuries, since the advent of science, most medicine has become a combination of art and science (both basic and applied, under the umbrella of medical science). While stitching technique for sutures is an art learned through practice, the knowledge of what happens at the cellular and molecular level in the tissues being stitched arises through science.

Prescientific forms of medicine are now known as traditional medicine and folk medicine. They remain commonly used with or instead of scientific medicine and are thus called alternative medicine. For example, evidence on the effectiveness of acupuncture is "variable and inconsistent" for any condition,[6] but is generally safe when done by an appropriately trained practitioner.[7] In contrast, treatments outside the bounds of safety and efficacy are termed quackery.


Medical availability and clinical practice varies across the world due to regional differences in culture and technology. Modern scientific medicine is highly developed in the Western world, while in developing countries such as parts of Africa or Asia, the population may rely more heavily on traditional medicine with limited evidence and efficacy and no required formal training for practitioners.[8] Even in the developed world however, evidence-based medicine is not universally used in clinical practice; for example, a 2007 survey of literature reviews found that about 49% of the interventions lacked sufficient evidence to support either benefit or harm.[9]

In modern clinical practice, doctors personally assess patients in order to diagnose, treat, and prevent disease using clinical judgment. The doctor-patient relationship typically begins an interaction with an examination of the patient's medical history and medical record, followed by a medical interview[10] and a physical examination. Basic diagnostic medical devices (e.g. stethoscope, tongue depressor) are typically used. After examination for signs and interviewing for symptoms, the doctor may order medical tests (e.g. blood tests), take a biopsy, or prescribe pharmaceutical drugs or other therapies. Differential diagnosis methods help to rule out conditions based on the information provided. During the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. The medical encounter is then documented in the medical record, which is a legal document in many jurisdictions.[11] Follow-ups may be shorter but follow the same general procedure, and specialists follow a similar process. The diagnosis and treatment may take only a few minutes or a few weeks depending upon the complexity of the issue.